Stacks are basically last in - first out (LIFO) queues and their use to hold data elements is known in the art. For example, Digital Equipment Corporation and Burroughs Corporation have used LIFO stack queues to hold data elements in several of their publicly announced products. The use of stacks by Programming has been widely described, for instance, "Operating System Principles" by Per Brinch Hansen, published by Prentice Hall, pp. 162, et seq.
Stacking in previous data processing systems has been utilized predominantly for data operands. However, it is known to store return instruction addresses of subroutines in a push-down stack for controlling sequential return to unfinished subroutines. It is also known to store subroutine return addresses in a main memory. The dynamic allocation of storage space for data is an accepted technique.